Image forming materials for transferring a photosensitive resin layer onto a substrate are known from, for example, JP-B-56-40824 (the term "JP-B" as used herein means an "examined published Japanese patent application"). Image forming materials of this type are used in the manufacture of printed circuit boards, intaglio or relief printing plates, name plates, multicolor printing proofs, offset printing plates, screen printing stencils, etc. These transfer materials are basically composed of a temporary substrate, a parting layer, and a photopolymerizable layer. Image formation using the transfer material is carried out by adhering the photopolymerizable layer to a permanent substrate, stripping the temporary substrate off the transfer material, exposing the photopolymerizable layer to light through the parting layer, and developing the exposed photopolymerizable layer to form an image on the permanent substrate. The parting layer serves as an oxygen barrier in favor of exposure in air. Having a very small thickness of from about 0.5 to 5 .mu.m, the parting layer does not adversely affect the resolving power.
However, where a permanent substrate to which a photopolymerizable layer is to be transferred has unevenness, air bubbles are apt to be entrapped between the substrate and a very thin photopolymerizable layer, resulting in insufficient transfer. For example, this is observed in the case of formation of a multicolor image as in the preparation of a color filter, in which the transfer of pixels of a first color is followed by the transfer of a photosensitive resin layer of a second color, and in the case where a dry resist layer is transferred to the copper surface of a copper-clad laminate having fine scratches or marks resulting from polishing as in the preparation of printed circuit boards.
JP-A-2-213849 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a transfer material having an intermediate layer of a polyvinyl alcohol derivative, etc. between a temporary substrate and a photosensitive resin layer. Provision of the intermediate layer aims at improvements in releasability of the temporary substrate and dissolving characteristics, with no consideration being given to transfer properties in the case where the transfer material is transferred to a permanent substrate having unevenness.
JP-A-63-309946 points out the occurrence of transfer failure due to insufficient adhesion of a transfer layer to a permanent substrate where the substrate has fine irregularities on its surface or where the substrate and/or the transfer layer have thereon fine particles such as dust. In order to prevent such transfer failure, the publication teaches the use of a compressive temporary substrate. This means is certainly effective but is still insufficient for preventing entrapment of air where a non-tacky photosensitive resin layer is transferred at room temperature to a substrate whose surface roughness is equal to the thickness of the photosensitive resin layer.
JP-A-5-72724 discloses a transfer method using a photosensitive transfer material comprising a temporary substrate, particularly a gelatin-coated plastic film, having thereon a thermoplastic resin layer, a parting layer, and a photosensitive resin layer in this order, in which the photosensitive resin layer is adhered to a permanent substrate, and the temporary substrate and the thermoplastic resin layer are then simultaneously stripped off to leave the photosensitive resin layer on the permanent substrate. According to this method, however, it is not always easy to control the release between the thermoplastic resin layer and the parting layer, which is a disadvantage in automating the release operation.
U.S. Pat. No. 5,292,613 discloses a photosensitive transfer material comprising a temporary substrate having thereon an alkali-soluble thermoplastic resin layer, an intermediate layer, and a photosensitive resin layer in this order. The transfer properties of this transfer material are still insufficient for achieving a high speed and a high yield in transfer, even at a high temperature, onto a permanent substrate whose surface roughness is equal to the thickness of the photosensitive resin layer. In addition, removal of the alkali-soluble thermoplastic resin layer with an alkali aqueous solution takes time, making it difficult to increase the speed of the whole line.
U.S. Pat. No. 5,292,613 discloses a photosensitive transfer material comprising a temporary substrate having thereon an alkali-soluble thermoplastic resin layer, an intermediate layer, and a photosensitive resin layer in this order. If the alkali-soluble thermoplastic resin layer comprises a soft resin or contains a large quantity of a plasticizer in an attempt to increase the transfer speed, fine wrinkles develop on the intermediate layer, formed on an alkali-soluble thermoplastic resin layer formed on a temporary substrate, and remain there as surface unevenness, called reticulation. Reticulation has been a hindrance to obtaining a smooth coating surface of a photosensitive resin layer formed thereon. It has therefore been difficult to achieve a high speed in transfer while preventing reticulation.